The present invention relates to image signal processing systems, and in particular relates to an image signal processing system correcting the brightness of an image which is photographed in a scene having a large difference in brightness.
Examples of the related art in this technical field include JP-A-2009-65711 (see the abstract). The subject of JP-A-2009-65711 is to correct the brightness of an input image so that an area having a local difference in brightness becomes distinct without uniformly using a photometry frame. As a solution of this subject, there was provided an image processing system, in which the photometry evaluation section 350 generates a photometry evaluation value indicative of the evaluated brightness of an image signal; the luminance area generation section 361 calculates a dark-side foot value and a bright-side foot value in the luminance distribution of an image with the average luminance in block; the spline generation section 362 handles the photometry evaluation value as the average luminance value and furthermore uses the dark-side foot value and the bright-side foot value to generate a tone curve by a spline curve; the gradation compression section 380 compresses the gradation of the luminance value based on the tone curve; the contrast correction section 390 corrects the contrast of the luminance value whose gradation has been compressed; and the gradational correction processing section 320 corrects the gradation of a pixel value of a non-linearly transformed RGB image based on the luminance value whose contrast has been compressed.